scholarly journals A GTN-like Model for Plastic Porous Materials

2014 ◽  
Vol 4 (6) ◽  
pp. 734-738
Author(s):  
L. Siad ◽  
S. C. Gangloff
Keyword(s):  
Constitutive Model ◽  
Yield Function ◽  
Isotropic Hardening ◽  
Extended Version ◽  
Gtn Model ◽  
Hardening Model ◽  
The Third ◽  
Third Stress Invariant ◽  
Stress Invariant ◽  
Good Agreement

An extended version of the well-known Gurson-Tvergaard-Needleman (GTN) isotropic hardening model is presented in this paper. The yield function of the proposed constitutive model possesses the distinctiveness to explicitly depend upon the third stress invariant. The presented constitutive model is used to analyze the necking of a round tensile bar. As long as softening initiation of specimen is not reached, the obtained numerical results highlight similarities and good agreement with those provided by the use of the GTN model. However, discrepancy shows up as soon as specimen failure starts.

Damage Theoretical Analysis of 2.5D C/SiC Composites under Tensile and Shear Loading

2010 ◽  
Vol 150-151 ◽  
pp. 330-333
Author(s):  
Yan Jun Chang ◽  
Ke Shi Zhang ◽  
Gui Qiong Jiao ◽  
Jian Yun Chen
Keyword(s):  
Constitutive Model ◽  
Damage Evolution ◽  
Yield Function ◽  
Shear Loading ◽  
Isotropic Hardening ◽  
Shear Tests ◽  
Energy Equivalence ◽  
Damage Constitutive Model ◽  
Sic Composites ◽  
Nonlinear Hardening

An anisotropic damage constitutive model is developed to describe the damage behavior of C/SiC composites. Different kinematic and isotropic hardening functions were employed in damage yield function to describe accurately the damage nonlinear hardening. The damage variable is defined by the principle of energy equivalence. The degradation of stiffness and the unrecoverable deformation induced by micro-crack propagation were considered in this model. The constants of constitutive model are identified and the damage evolution processes under tensile and shear loading. Uniaxial tension and shear tests have been used to valid the constitutive model to C/SiC composites.

DUCTILE DAMAGE ANALYSIS BASED ON A J3-GTN-LIKE MODEL

2011 ◽  
Vol 03 (04) ◽  
pp. 189-215 ◽  
Author(s):  
LARBI SIAD
Keyword(s):  
Constitutive Model ◽  
Yield Function ◽  
Shear Loading ◽  
Isotropic Hardening ◽  
Single Element ◽  
Mapping Algorithm ◽  
Failure Initiation ◽  
Fully Implicit ◽  
Return Mapping ◽  
Return Mapping Algorithm

A GTN-like model which yield function explicitly depends upon the third stress invariant is first described in this paper. Subsequently, a fully implicit stress integration procedure of this constitutive model based on the return-mapping algorithm is developed. The validity and the performance of the implementation of the considered algorithm within a finite element code are checked through simulations of single element test and three-element test under hydrostatic tensile conditions and simple shear loading as well. Afterwards, as a numerical example, the presented constitutive model and, for the purpose of comparison, the GTN isotropic hardening model, are used to analyze the classical tensile test of axisymmetric notched specimens. The obtained results highlight similarities, good agreement between both models as long as failure initiation of specimen is not reached, and discrepancy as soon as failure of specimen starts.

A Plasticity Model for Metals With Dependency on All the Stress Invariants

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
George Z. Voyiadjis ◽  
S. H. Hoseini ◽  
G. H. Farrahi
Keyword(s):  
Yield Criterion ◽  
High Strength ◽  
Experimental Tests ◽  
Deviatoric Stress ◽  
Cyclic Behavior ◽  
Isotropic Hardening ◽  
Plasticity Model ◽  
Mapping Algorithm ◽  
The Third ◽  
Stress Invariant

Recent experiments on metals have shown that all of the stress invariants should be involved in the constitutive description of the material in plasticity. In this paper, a plasticity model for metals is defined for isotropic materials, which is a function of the first stress invariant in addition to the second and the third invariants of the deviatoric stress tensor. For this purpose, the Drucker–Prager yield criterion is extended by addition of a new term containing the second and the third deviatoric stress invariants. Furthermore for estimating the cyclic behavior, new terms are incorporated into the Chaboche's hardening evolution equation. These modifications are applied by adding new terms that include the effect of pervious plastic history of deformation on the current hardening evaluation equation. Also modified is the isotropic hardening rule with incorporating the effect of the first stress invariant. For calibration and evaluation of this plasticity model, a series of experimental tests are conducted on high strength steel, DIN 1.6959. In addition, finite element simulations are carried out including integration of the constitutive equations using the modified return mapping algorithm. The modeling results are in good agreement with experiments.

On the Development and Identification of Phenomenological Damage Models - Application to Industrial Wire Drawing and Rolling Processes

2013 ◽  
Vol 554-557 ◽  
pp. 213-226 ◽  
Author(s):  
Trong Son Cao ◽  
Christian Bobadilla ◽  
Pierre Montmitonnet ◽  
Pierre Olivier Bouchard
Keyword(s):  
Stress Tensor ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Wire Drawing ◽  
Damage Models ◽  
The Third ◽  
Third Stress Invariant ◽  
Lode Angle ◽  
Stress Invariant ◽  
Angle Parameter

The continuum thermodynamics-based Lemaitre damage model is nowadays widely used to deal with coupled damage analyses for various mechanical applications (e.g. forming process simulations). However, such a model, which only accounts for the stress triaxiality (the ratio between the first and the second invariants of stress tensor) has been found to give incorrect results under shear dominated loading (in terms of damage location as well as risk of crack). Several recent studies have demonstrated the importance of the third stress invariant in damage prediction; the Lode angle parameter is generally used to include it. The idea is to describe completely the stress state in damage model’s formulations, which is defined by the equivalent stress, the stress triaxiality ratio and the Lode angle parameter. This later parameter has proved to have an important influence on ductile damage under low stress triaxiality. Xue’s coupled damage model accounts for the third invariant of the deviatoric stress tensor, allowing a better balance between respective effects of shear and elongation on damage. Some extensions of more physically based damage models, such as the Gurson-Tvergaard-Needleman model, have also been presented to account for this influence of the third stress invariant. In the present work, the phenomenological damage models have been implemented in Forge® Finite Element (FE) software to investigate ductile damage occurring during industrial forming processes. This paper presents the comparative study of Xue’s model and Lemaitre’s model. A complete procedure is detailed to identify the material and damage parameters from experimental mechanical tests on high carbon steel. This identification process has been carried out both for Lemaitre’s coupled damage model and Xue’s coupled damage model. Application to wire drawing followed by flat rolling shows that in such shear-inducing processes, these models predict damage at different locations, due to their different emphasis on shear with respect to elongational strain damage.

Sign in / Sign up

Export Citation Format

Share Document